ground floor, ground zero, first floor

When I traveled to the European countries, I saw the "first floor" marked in an elevator is actually the second story of the building. So where is the actual first floor? How do you call the first story of a building?

Sorry for bringing this up, but it seems to me logic to place my question here.

What would you call to floors which are underground? Say you would have -1, -2, and -3, all below the ground floor (or first floor, whatever you call to the floor which is leveled with the outside pavement )?

Would you call to -1 first floor below ground/first floor? And so on to the floors below this one?

Sorry for bringing this up, but it seems to me logic to place my question here.

What would you call to floors which are underground? Say you would have -1, -2, and -3, all below the ground floor (or first floor, whatever you call to the floor which is leveled with the outside pavement )?

Would you call to -1 first floor below ground/first floor? And so on to the floors below this one?

Click to expand...

From my limited experience with buildings like that, they have floors/levels labeled as B1, B2, B3 etc for basement 1, basement 2 etc. (If they are levels for car parks then they might be labeled P1 , P2 etc)